The invention of the prior art disclosed by R.O.C. (Taiwan) patent number 595342 with a title of office desk structure, issued to the applicant, is for adjusting the height of the desk top of an office desk. The invention comprises a desk top, a base frame having a base and a sleeve mount, and a synchronic elevating mechanism installed at a selected place within the desk body. The bolt of tile prior art is inserted in the sleeve mount of the base frame. The transmission shaft of the invention comprises a bevel gear for transmission and a bevel gear for elevation. The invention further includes a turning handle for driving the elevating mechanism whereby height adjustment of a desk can be realized.
The elevating mechanism of the prior art, which utilizes the engagement of a bevel gear for transmission and a bevel gear for elevation, has the following disadvantages.
1. The engagement of the bevel gears has a small interface and therefore is easy to collapse.
2. The combination of the bevel gears may contain an error in the engagement, which will result in noises when operated. It may also cause off-axis of at least one bevel gear and consequently a collapse of the engagement.
3. The handle is installed at a fixed position, and therefore the operation of the handle may be hindered in a tight space.